Stain resisting cobalt alloy



Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE FREDERICK MI.BECK-ET, OF NEW YORK; N. 'Y., ASSIGNOR TO ELECTRO METALLURGICAL COMPANY,A. CORPORATION OF WEST VIRGINIA s'mm nnsrsrme 001mm ALLOY N0 Drawing.

This invention relates to stain resisting alloys containing as essentialconstitutents the metals iron, chromium, manganese and cobalt.

In application serial No. 435,957 filed by me on March 14, 1930, I havedisclosed stain resisting ferrous alloys containing not less than aboutsixteen per cent nor more than about twenty-two per cent of chromium,and not less than about six per cent nor more than about sixteen percent of manganese. I have shown that when these alloys contain not morethan about three tenths per cent carbon and preferably not more thantwelve hundredths .per cent of this element, they possess excellentworkabllity and \are adapted to deep drawing operations. In applicationvSerial No. 448,428 filed simultaneously herewith I have shown that theiron-chromium-manganese compositions are more resistant than theworkable stainresisting iron-chromium-nickel alloys to attack, by gassescontaining sulphur com.- pounds and I have also shown that an additionof cobalt to the iron-chromium-manganesebase will markedly increase itsstrength at elevated temperatures ,without destroying its workingproperties or its resistance to sulphur-bearing gases and othercorrosive influences. The invention claimed herein is the. group ofalloys produced by so combining iron, chromium, manganese and cobalt.

The high temperature strength is in-. creased by cobalt percentagesas-low as one per cent and perhaps even lower. With higher percentagesof cobalt the efl'ect is more pronounced but as the cobalt rises aboveabout five per cent the high temperature strength is not additionallygreatly in creased. Cobalt percentages between the approximate limits ofone per cent and ten per cent are regarded as the most useful.

The following examples show the efiect Application filed April 29,

1030. Serial n0. 448,420.

of cobalt on the strength of the chromeiron-manganese alloys at 900 C.

Percent Percent Percent Percent Percent Percent in. max. red. of 1' Mn 0C0 8m 01. n 2' area 11.17 1 r 8. 09 0. 00 e. 250 4.1 00. 17. 19 10. 270. 11 9, 000 43 72. g 17. 30 8. 60 0. 09 2. 14. 500 44 72. 80 18. 8. 800. 12 4. 97 19, 120 36 73. 17. 36 8. 76 0. 14 8. 85 18, 250 45 65. 4017. 56 8. 74 0.15 13. 95 21, 400 25 65. 10

In the tests tabulated above th'e test pieces were held at 900 C. forabout forty minutes before applying the load and the load was appliedgradually and at a uniformly mcreasing rate so that about twenty minuteswas required torupture the test piece.

The following examples show the efl'ect of cobalt on. the strength ofthe chromeiron-manganese allows at 600 C.

. Lbs./sq.ln.

Per- Pe f- Per- Po a? cent cent cent can? Mn o 00 mm Max. 51.1112" pointstress m 11.10 10.21 0. 1 20,000 30,150 41 vis per cent carbon have adistinct field of utiland carbon, the carbon content being ity. ,Wherethe alloy is to be subjected to not more than about 0.12%;the remainderdeep drawing or like severe cold working being chiefly iron.

- operation it is often advantageous to cool it 3 in air or quench itfrom temperatures in the vicinity of 1000 C. to 1150" C.

A principal field of application for the herein described alloys is inthe thermal decomposition of hydrocarbon material, for example thecracking of petroleum fractions to produce gasoline. Such decompositionsare ordinarily carried out in tubes and the latter may be subjected at ahigh temperature to oxidizing conditions on the outside andsimultaneously to the action of sulfur compounds associated with thematerial being cracked and contained within the tubes. The alloys of theinvention are in all respects admirably adapted'to the fabricationoftubes for such operations, and they are equally suitable for makinthetubular condensers in which the crac ed products are usuallyliquefied.

- I claim:

1. A ferrous alloy containing chromium not less than about sixteenpercent nor more than about twenty-two per cent, manganese not less thanabout six per cent nor more than about sixteen per cent and cobalt notless than about one per cent nor more than about ten per cent, andcarbon, the carbon content being, not more than three tenths of one percent; the remainder being chiefl iron.

2. A stain resisting ferrous alloy aving deep drawing properties andcontaining" chromium about elghteen percent, manganese about ei ht percent, carbon, the content of carbon ieing, not more than twelvehundredths per cent and about five per cent of cobalt; the remainderbeing-chiefly iron.

3. An article of manufacture sub ect to the action of hot sulfur-bearingases, said article being composed of a errous alloy containing chromiumnot less than about 16% and not more than about 22%, manganese not lessthan about 6% and not more than about 16%, cobalt not less than 1% andnot more than aboutl0%, and carbon, the carbon content being not morethan about 0.3%; the remainder being chiefly iron.

4. An oil cracking tube composed of a ferrous alloy containing chroniumnot less than about 16% and not more than about 22%, manganese not lessthan about 6% and not more than about 16%, cobalt not less than about 1%and not more than about 10%, and carbon, the carbon content being notmore than about 0.3%.; the remainder a being chiefly iron. 5, An oilcracking tube composed of a ferrous alloy containing chromium not lessthan about 16% and not more than about 22%, manganese not less thanabout 6% and not more than about 16%, cobalt not less '65 than about 1%and not'more than about In testimon whereof, I aflix my signature.

F EDERICK M. BECKET.

